The Thermostat

Just like your body needs to warm up when you begin to exercise, your car's engine needs to warm up when it starts its exercise. The thermostat provides control for your engine's warm-up period. The thermostat is located between the engine and the radiator. This little temperature-sensitive spring valve stays closed during engine warm-up. When the thermostat is closed, it prevents coolant from leaving the engine and circulating through the radiator until the correct running temperature is reached. The correct running temperature for most engines is between 180 degrees F and 200 degrees F. When the right temperature is reached, the spring valve opens, allowing coolant to circulate through the radiator to be cooled-- almost like our bodies begin to perspire after we've warmed-up. The temperature at which the thermostat is designed to open is called its rating, and may be stamped on the body. The 180 Degrees F thermostat begins to open at (you guessed it!) 180 Degrees F and is fully opened at 200 degrees F. Different engines use different temperature thermostats. Some high range thermostats maintain engine operating temperatures above 200 degrees F. This causes the engine to burn up more pollutants and aids in emissions control. However the range for your thermostat depends on the type of your engine, load requirements, weather, and other variables. Most thermostats are the "pellet" type; the name comes from the wax pellet that expands as the engine coolant warms. The pellet's expansion forces the valve open. Thermostats occasionally get "stuck shut" which cuts off the cooling capacity of the radiator, at least partially. This often occurs after an engine has overheated for some other reason, such as when the water pump fails, or if a large coolant leak develops. For this reason, car makers usually place the thermostat in an accessible position. Depending on the air temperature, the engine should take from five to fifteen minutes to warm up. If your engine takes a long time to warm up, or if it always runs hot, you might need to test the thermostat. A malfunctioning thermostat can cause excessive engine wear and waste fuel. A good time to have your thermostat checked is just before summer or winter.